The present application is directed to modes of control for a personal transporter utilizing an electrical power source.
Dynamically stabilized transporters refer to personal vehicles having a control system that actively maintains the stability of the transporter while the transporter is operating. The control system maintains the stability of the transporter by continuously sensing the orientation of the transporter, determining the corrective action to maintain stability, and commanding the wheel motors to make the corrective action. If the transporter loses the ability to maintain stability, such as through the failure of a component, the rider may experience discomfort at the sudden loss of balance. For some dynamically stabilized transporters, such as those described in U.S. Pat. No. 5,701,965, which may include a wheelchair for transporting a disabled individual down a flight of stairs, it is essential, for the safety of the operator, that the vehicle continue to operate indefinitely after detection of a failed component. For other dynamically stabilized transporters, however, the operator may readily be capable of safely dismounting from the transporter in case of component failure. It is desirable that control modes be provided for such vehicles from which the operator is capable of safely dismounting in case of mishap.
In accordance with preferred embodiments of the present invention, there is provided a method for maintaining traction between wheels of a transporter and an underlying surface. The method has the steps of:
(a) comparing acceleration of a wheel with a specified pre-set value;
(b) setting a slip condition flag based on the acceleration of the wheel;
(c) reducing the torque applied to the wheel based on the slip condition flag;
(d) determining a value of a dynamic characteristic of the wheel; and
(e) clearing the slip condition flag based on the value of the dynamic characteristic of the wheel.
In accordance with alternate embodiments of the invention, the dynamic characteristic may be a moment of inertia or an inverse of a moment of inertia. The step of determining the dynamic characteristic may include dividing the acceleration by a commanded torque applied to the wheel. The step of reducing the torque applied to the wheel may include reducing the torque to zero, as well as slewing the torque incrementally.
In accordance with yet further embodiments of the invention, a device is provided for correcting wheel slippage on a vehicle. The device has a sensor for monitoring wheel speed, a differentiator for calculating wheel acceleration based on change in wheel speed, a comparator for comparing the wheel acceleration with a pre-set value and for setting a slip condition flag, and a controller for reducing any torque applied to the wheel, such that torque continues to be reduced until the slip condition flag is cleared.